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How is set() implemented?
...zation(s) that exploit this lack of values
So basically a set uses a hashtable as its underlying data structure. This explains the O(1) membership checking, since looking up an item in a hashtable is an O(1) operation, on average.
If you are so inclined you can even browse the CPython source code...
Bash empty array expansion with `set -u`
...-} or ${arr[@]:0}, are not safe across all major versions of Bash.
As the table below shows, the only expansion that is reliable across all modern-ish Bash versions is ${arr[@]+"${arr[@]}"} (column +"). Of note, several other expansions fail in Bash 4.2, including (unfortunately) the shorter ${arr[...
Can hash tables really be O(1)?
It seems to be common knowledge that hash tables can achieve O(1), but that has never made sense to me. Can someone please explain it? Here are two situations that come to mind:
...
Which is the fastest algorithm to find prime numbers?
...e needed in code, perhaps when you need to
dynamically find a prime hash table size within certain ranges. If N
is something on the order of 2^30, do you really want to do 30000
division tests to search for any factors? Obviously not.
The common practical solution to this problem is a sim...
Passing arguments forward to another javascript function
...lready supports spread operator is FF at the moment. See the compatibility table for a complete, up to date data: kangax.github.io/compat-table/es6/#spread_%28...%29_operator
– TMG
Aug 13 '15 at 8:37
...
What's the difference between echo, print, and print_r in PHP?
...ing
No return value
var_export()
Outputs a human-readable and PHP-executable representation of any one value
Accepts not just strings but other types including arrays and objects, formatting them to be readable
Uses a different output format to both print_r() and var_dump() - resulting output is...
Browsers' default CSS for HTML elements
...}
li { display: list-item }
head { display: none }
table { display: table }
tr { display: table-row }
thead { display: table-header-group }
tbody { display: table-row-group }
tfoot { display: table-footer-group }
col ...
What is the error “Every derived table must have its own alias” in MySQL?
...
Every derived table (AKA sub-query) must indeed have an alias. I.e. each query in brackets must be given an alias (AS whatever), which can the be used to refer to it in the rest of the outer query.
SELECT ID FROM (
SELECT ID, msisdn F...
How do I check in JavaScript if a value exists at a certain array index?
...guage and it would be inefficient for certain code. They're probably hash tables or some hybrid mixture of strategies, and undefined ranges of the array probably aren't allocated their own memory. Nonetheless, JavaScript the language wants to present arrays of array.length n as having n members an...
How do I move a table into a schema in T-SQL
I want to move a table into a specific Schema using T-SQL? I am using SQL Server 2008.
2 Answers
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